The present disclosure generally relates to a device and methodology for occluding arterial and venous blood vessels under a variety of pathologic conditions.
Many endovascular devices exist for occluding blood flow including coils, detachable balloons, and most recently expandable mechanical occlusive devices with or without coverings impervious to blood flow. Coils can be covered with fibers or coated with material such as hydrogel to enhance clot formation. Despite these features many coils are often required to occlude blood flow increasing procedure time and potentially cost. Coils can also be unreliable with regards to their geometry and vascular space filling properties after deployment. In addition coils and or clot can easily migrate distally under high flow condition such as arteriovenous fistula in the lungs or elsewhere in the body. Blood vessels occluded by coils can reopen or recanalize as has been reported in pulmonary arteriovenous fistula. Detachable balloons can be difficult to navigate through blood vessels and can prematurely detach. Premature balloon detachment can lead to migration and occlusion of normal blood vessels resulting in complications. Balloons can deflate over time resulting in recurrence of the treated vascular pathology such as has been reported in caroticocavernous fistula. More recently detachable uncovered and membrane covered expandable mechanical occlusive devices have been developed in an attempt to occlude blood flow more rapidly, permanently, and with more spatial precision; commonly referred to as vascular plugs. These include the uncovered detachable Amplatzer vascular plug which is made of a self-expanding Nitinol mesh, it is delivered through catheters or sheaths of varying size, inciting vessel thrombosis. This device may not immediately lead to thrombosis particularly in patients with clotting disorders, requiring more than one device. The device can be difficult to deliver and precisely deploy. In addition the device may not provide long-term occlusion, which has been reported in pulmonary arteriovenous fistula in particular. Covered devices such as the MVP microplug can provide immediate occlusion with good long-term occlusion in early studies. The MVP is the only covered plug that can be delivered through a microcatheter, particularly advantageous when navigating through tortuous anatomy and smaller vessels. The largest MVP microcatheter deliverable covered plug can only treat vessels up to 5 mm in diameter, a distinct disadvantage. Larger MVP covered plugs require delivery through 4 or 5 French catheters depending on the target vessel size; these larger catheters are often too big and rigid to easily traverse the desired vasculature. The use of these larger 4 and 5 French catheters to target the more distal vasculature can lead to technical failures, vessel spasm and vascular injury. Vessels up to 7 mm can be treated through a 4 French catheter while vessels up to 9 mm can be treated through a 5 french catheter with the MVP device. The device may not be ideal for high flow situations with possible migration considering it's small footprint and vessel anchoring capabilities. Precise measuring or sizing relative to the target vessel is important. The relatively small length rigid nitinol frame is best suited for straight vessel segments or horizontal deployment zones.
It would be desirable to occlude larger vessels than 5 mm through a microcatheter with a covered plug, not currently possible with available devices such as the MVP. Microcatheters are usually manufactured with two different size internal diameters, namely 0.021 inch (standard) and 0.027 inch (high-flow). Larger 4 French and 5 French diagnostic catheters typically have internal diameters of 0.040 inch and 0.046 inch respectively. 5 French diagnostic angiographic catheters are typically used to catheterize the origins or proximal aspects of the major branch vessels arising in the neck, chest, abdomen, pelvis and lower extremities; and can accommodate both standard and high flow microcatheters. These larger 5 French diagnostic catheters are often difficult to advance more distally into the primary or secondary aortic branch vessels such as the hepatic artery, splenic artery, renal artery, internal carotid artery and hypogastric artery to name a few. It would be clinically advantageous to be able to occlude vessels larger than 5 mm with a microcatheter deliverable covered vascular plug, advanced through a 5 French angiographic catheter. The target vessels for occlusion are often larger than 5 mm, precluding the use of a microcatheter for vascular plug delivery by current means and methods. In addition, microcatheters are advantageous for traversing tortuous anatomy, often difficult or impossible with larger 5 French catheters. Venous embolization often entails occluding even larger caliber vessels than arteries, often necessitating larger guiding catheters or sheaths for device delivery, such as the uncovered Amplatzer plugs.
It is preferable on many occasions to occlude a blood vessel on both the upstream and downstream sides relative to a given arterial or venous vascular pathology, i.e. to mechanically occlude a vascular segment. This can be difficult and or cumbersome to achieve with current available devices. For example it can be desirable to occlude a fusiform aneurysm or abnormal ballooning of a blood vessel on both sides since the aneurysm might still fill or stay open after just upstream occlusion of the artery. A fusiform aneurysm is spindle or football shaped; it bulges or balloons out on all sides of the blood vessel. Flow can reverse through collateral filling in the downstream portion of the artery relative to the fusiform aneurysm, after just upstream occlusion by a vascular plug, thereby maintaining patency of the aneurysm. Initial occlusion of the downstream portion of the vessel relative to the fusiform aneurysm can result in increased flow and pressure in the aneurysm resulting in rupture. It is generally safer under these circumstances to occlude distally only under the conditions of proximal flow and pressure control (flow arrest) to prevent possible vessel rupture.
It is often desirable to primarily occlude saccular intracranial or peripheral saccular aneurysms while simultaneously sparing the parent vessel from which it arises. A saccular aneurysm is a blind ending vascular outpouching or sac, which arises only from one side of the blood vessel. The occlusion or closing of a saccular aneurysm is often accomplished by placing multiple coils of varying shapes and sizes directly within the aneurysm sac. Although effective this process can be cumbersome when using current methods, particularly for larger aneurysms, requiring multiple coils to fill the aneurysm sac. In addition the coils can compact overtime with aneurysm recurrence, typically occurring at the aneurysm neck or site of connection with the parent vessel. Coils can also prolapse into the parent vessel if the aneurysm neck is wide. It has been shown that disruption of flow within the blind ending aneurysm sac leading to thrombosis can be achieved even with uncovered porous or mesh like intra-aneurysmal space filling devices, often called flow disruptors. It would desirable to have an intra-aneurysmal space filling occlusive device that could approximate the spherical or ellipsoid shape typical of a saccular aneurysm with either a single or limited number of devices in order to more rapidly, effectively, and perhaps more permanently occlude the aneurysm sac.